Re: A partial black hole?

On 2008-02-23, Mike Huskey <mikehsk@[EMAIL PROTECTED]
> wrote:
> Nothing can escape the gravity of a black hole, where escape
> velocity is greater than the speed of light.  But what if you have
> two black holes closely orbiting each other. Doesn't the gravity of
> the two objects cancel out between each other?

It's nowhere near that simple. Two black holes orbiting that closely
will be revolving incredibly quickly, and the field around them will
be very difficult to model. Much of their orbital energy will be
radiated away as gravity waves and they will quickly merge into one
rapidly spinning black hole.

I think (but am not sure) that you are thinking of black holes as
being extended objects with some sort of spherical surface.
Mathematically, they are pointlike singularities with an immaterial
event horizon.

The horizon is defined as being the boundary of the region within
which all timelike paths intersect the singularity. In the case of
close binary black holes, the horizon is likely to have a more complex
shape than two spheres, and will likely change rapidly as the black
holes radiate energy and spiral inward.


> I would guess that anything that does escape would be quickly
> recaptured.

If it could escape without locally exceeding the speed of light, it
was by definition not within the event horizon.


- Tim